Calculate standard deviation
Submitted by mpavas on Mon, 12/03/2012  01:19
I came across this question and I do not know how to make the calculation. I know the values of sigma. The right answer is 0.4. This is question from Scordo
A process in a mobile phone manufacturing project has an upper control limit of 0.12. What is the standard deviation of the process if the upper control limit is set at 3 Sigma?

0.5

0.4

0.12

0.36
Forums:
sspawar
Mon, 12/03/2012  04:34
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3sigma =0.12Hence sigma (SD)
3sigma =0.12
Hence sigma (SD) = 0.04,
one point decimal error in question, such errors I observed in real exam also. but very very rare, Be careful.
happyinlove505
Mon, 12/03/2012  05:15
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3sigma =0.12Hence sigma (SD)
Hello sspawar,
just wanted to clarify: do you assume that lower control limit is 0.00?
mpavas
Mon, 12/03/2012  14:52
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Have you used the
Have you used the below formula?
Sigma = 0.12 /3
rajesh.thallam
Mon, 12/03/2012  15:31
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Control Charts Upper Limits
Control limits are generally +3sigma (PMBOK pg196)
Here upper control limit is .12 i.e. 3sigma = .12
=> sigma (Standard deviation) = .12/3 = .04
sspawar
Tue, 12/04/2012  05:14
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Now it is more clear
Rajesh has clearified, there is nothing like 0, as LCL(lower control limit).
if SD is 0.04
LCL will be 3sigma = 0.12
UCL will be +3sigma = +0.12

mpavas
Sun, 12/09/2012  04:29
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thanks for the clarification.
thanks for the clarification. U guys cleard the doubts